The statements in this section merely provide background information related to the present disclosure and may not constitute a prior art.
Video data compression technologies include the standards of H.261, H.263, MPEG-2, and MPEG-4. According to the standards of the video data compression technologies, each image is encoded by partitioning the same into fixedly sized macroblocks which are composed of rectangular 16×16 pixel areas of a luminance or luma component and rectangular 8×8 pixel areas of a chrominance or chroma component. All of the luminance and chrominance components of the respective macroblocks are spatially or temporally predicted, and the resultant predicted residuals undergo transform, quantization, and entropy coding to be transmitted.
In a block mode used in an existing video encoding apparatus, no more information is encoded than a flag for indicating that a block to be currently encoded is a block using a predicted motion vector and having no transform coefficient to be encoded. Then, in the case of a block using no predicted motion vector or having a transform coefficient to be encoded, block type information and prediction information (a difference vector between a motion vector and a predicted motion vector and a reference picture index) are encoded and the transform coefficient is also encoded.
However, in the aforementioned known video compression technologies, the inventor(s) has experienced that there are problems with achieving (i) an efficient encoding of such blocks that have only a differential motion vector as data to be encoded but no transform coefficient to be encoded, or (ii) an efficient encoding of such blocks that have no differential motion vector but only the transform coefficient to be encoded. The inventor(s) has also experienced that there is a difficulty with achieving an efficient encoding of various information used for encoding videos and the like.